Atlas Copco SECOROC COP 54 Manual - Página 7

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Flushing — Air-blowing
To avoid wasteful re-crushing and the risk of jam ming, drill cuttings
must be fl ushed out of the drill hole at the same rate as new cuttings
are produced. It is good drilling practice to clean out the hole at regular
intervals by means of air-blowing. This is especially import ant in non-
consolidated formations and when there is a danger of the hole wall
collapsing. Air-blowing is done by lifting the hammer off the bottom of
the hole (fi g. a) and running the feed back and forth.
N.B. Rotation must always be to the right. The impact mechanism
stops as soon as the hammer is lifted and the bit drops downwards,
which causes a considerable volume of air to fl ow through the hammer
and fl ush-out the hole. When the hammer is lowered back on to the
bottom of the hole, the bit is pressed back into the impact position,
which re-starts the impact mechanism (fi g. b).
N.B. The hammer can fl ush more air than the compressor can
deliver. This means that the air supply from the compressor should
be restricted (by means of the impact-control valve) if the air-blowing
sequence is activated longer than 3–5 seconds.
a
b
WARNING
Always wear goggles during drilling. The backward-directed fl ush-
ing air from the top sub contains drill cuttings and oil residue which
can injure the eyes.
Extra fl ushing
The need for extra fl ushing is greater at low working pressures and in
diffi cult drilling conditions, e.g. when there is a high infl ux of water into
the hole. Extra fl ushing can be introduced by changing the valve in
the top sub (fi g. c). This gives extra fl ushing air where it is usually
needed most, i.e. at the reduction in diameter between the hammer
and the drill pipes.
The fl ushing holes in the top sub are directed backwards (fi g. c),
which prevents the air jets from damaging the hole wall. Naturally,
extra fl ushing will increase the air consumption of the drilling system
(see table). For this reason, it is advisable to fi rst check the delivery
capacity of the compressor.

Changing the valve

To change the valve, the top sub of the hammer must be removed
(fi g. d).
Remove the circlip E and washer F with the aid of the compressing
tool K.
Take out the valve D from the top sub A using the handle of the
compressing tool (fi g. e) and remove O-ring H. Remove the rubber
sleeve C and O-ring G from the valve.
Replace with a suitable valve (see table), or drill holes in the
original valve (fi g. f).
Change the rubber sleeve and O-rings if necessary.
Smear the valve, rubber sleeve and O-rings with silicone grease.
Fit the rubber sleeve C and O-ring G back on to the valve.
Make sure that the rubber sleeve is correctly fi tted. A leaking
rubber sleeve can cause serious damage to the hammer.
Check the location and condition of O-ring H in the bottom of the
top sub.
Slide the valve back into its position in the top sub.
Fit the O-ring I into the groove on the valve and place washer F
over the O-ring.
Use the compressing tool K to compress the O-rings H and I.
Tighten/compress until the circlip E can be fi tted into the circlip
groove.
The valve should now be held fi rmly in place and not be moveable
axially.
Fit the top sub back on to the hammer.
Check the sealing effi ciency of the check valve, as described in the
paragraph "Dirt in the hammer" on page 9.
N.B. Always check the shimming of the hammer when re-fi tting the
top sub. Follow the "shimming" instructions on page 10.
d
c
A
f
E
F
I
J
B
D
G
C
K
COP 34/44/54/64.2/64.3/84.2L 3161-1280-80
COP 84
e
D
C
Handle of compressing tool
42 mm
(COP 84)
Additional air consumption
Number of
holes × Ø
2 × 2 mm
2 × 3 mm
2 × 4 mm
4 × 2 mm
4 × 3 mm
4 × 4 mm
H
A
E
F
I
3161-1290-80
6 bar
10,5 bar 16 bar
5 l/s
10 l/s
15 l/s
12 l/s
24 l/s
31 l/s
21 l/s
42 l/s
53 l/s
10 l/s
20 l/s
30 l/s
24 l/s
48 l/s
62 l/s
42 l/s
84 l/s
106 l/s
7